The invention relates to an injection molding machine comprising a substantially C-shaped machine frame, on one limb of which is mounted a stationary mold mounting plate and on the other limb of which is mounted a closing mechanism for driving a movable mold mounting plate, wherein the free ends of the limbs of the machine frame, which are not connected by frame beams, deform under the influence of the closing force which occurs during the closing operation, and wherein arranged between at least one mold mounting plate and the machine frame is a hinge portion which includes a bar portion extending in the longitudinal direction of the machine, which hinge portion is deformed when the closing force is applied whereby the mold mounting plate is tilted relative to the associated limb of the machine frame.
Insofar as injection molding machines without frame beams have been proposed in earlier decades, the attempt has generally been to minimise the deformation of the C-shaped machine frame, which occurs under the influence of the closing force. Machines without frame beams only became of noteworthy practical significance however since designs have changed over to permitting a certain degree of deformation of the machine frame and compensating for that deformation by suitable measures. In that respect it is possible to permit deformation as between each of the two mold mounting plates and the associated limb of the machine frame, which deformation provides precise compensation for the spreading effect in respect of the limbs of the machine frame, so that the mold separation plane does not experience a change in its vertical position when the closing pressure is applied. In that respect the arrangement may be such (see EP 0 722 820 A1) that the upper end of the limb of the machine frame pivots in opposite relationship to the limb itself. In contrast, improved localisation of the pivot axes is achieved i- separate deformable holding portions are fitted between the mold mounting plates and the machine frame, as is shown in DE 295 16 398 U1.
In the case of the beam-less injection molding machine in accordance with EP 0 311 133 B, which in the meantime has become the classic design configuration, it is possible to manage with one pivot axis insofar as the stationary mold mounting plate is rigidly connected to the machine frame and the movable mold mounting plate is mounted tiltably so that it can also perform the pivotal movement that the fixed mold mounting plate experiences under the influence of the closing force. FIGS. 3 through 6 of AT 400 022 B show a corresponding structural configuration corresponding to the definition set forth in the opening part of this specification.